https://www.pumpsandsystems.com/valves/basics-check-valves
A swing check is the typical check used in the majority of hydronic systems
due to its ability to be a full port and not impede flow
Swing Check Valve
This is probably the most common check valve in use today and is a
full port design, meaning the disc, when fully open, is out of the flow stream. This style of check valve is a good choice in applications that have a high percentage of solids and a lower on/off cycle count. Due to the travel distance of the disc, swing check valves close slowly. This causes the last push of reverse flow to slam the disc closed, resulting in a huge pressure spike, causing water hammer. Water hammer is a pressure surge when a fluid in motion is forced to stop or change direction suddenly, causing a pressure wave in the pipe. This pressure wave can cause major problems from noise and vibration to pipe collapse.
Silent Spring-Assisted Axial Flow Check Valve
These full flow valves typically incorporate a center guided stem-disc assembly along with a compression spring. This means the disc stays in the flow stream. The media flows around it and does not require manual or automated assistance to operate. When the pump is running, the valve is open. When the pump shuts off, the valve closes slightly before the reversal of fluid flow, due to the compression spring force acting on the disc, which nearly eliminates water hammer.
Image 3. Silent spring-assisted axial flow check valve
Most requests for check valves take into consideration the line size and pressure class alone, as media pressure and flow can vary dramatically where pipe designs are oversized for future concerns or undersized due to lack of or incorrect information. This is not always the best way when deciding which style of valve to use in a system. Other things to consider are working pressure, flow rate, the specific gravity of the media and temperature. An analysis of the system design is highly recommended. It is necessary to understand why valves fail and the root causes. The most common failure is due to excessive wear of the internal parts of the valve. Springs, discs and stems wear prematurely by not being held steady during operation. When the disc is not stable due to insufficient flow to hold it in the full open position, chattering can occur.
What is Meant by Check Valve Sizing?
Sizing a center guided valve is not difficult. Along with the pipe size, pressure class and type of valve required (flanged, wafer, etc.), users need the actual working pressure, flow rate, media type, temperature and the specific gravity of the media. It may be as simple as building the valve with a lighter spring to allow the valve to fully open. In order for the valve to reach the full open position, it may need a lift limiter to reduce how far the disc travels. When the valve is 100 percent open, it will be stable in the flow and will result in reduced premature wear and failure by eliminating the effects of chatter. It is very important to remember that these valves are designed to the actual flow values and not to the line size. A properly sized valve will be in either the full open or closed positions.